Textbook Question
Define satellite DNA. Describe where it is found in the genome of eukaryotes and its role as part of chromosomes.
Ch. 11 - Chromosome Structure and DNA Sequence Organization
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 11, Problem 16
Assume that a viral DNA molecule is a 50-µm-long circular strand with a uniform 20-Å diameter. If this molecule is contained in a viral head that is a 0.08-µm-diameter sphere, will the DNA molecule fit into the viral head, assuming complete flexibility of the molecule? Justify your answer mathematically.
Verified step by step guidance1
Convert all given dimensions to consistent units, preferably micrometers (µm). For example, convert the DNA diameter from angstroms (Å) to micrometers using the conversion factor: 1 Å = 10\textsuperscript{-4} µm.
Calculate the volume of the viral DNA molecule by treating it as a cylinder with length equal to the DNA length and diameter equal to the DNA diameter. Use the formula for the volume of a cylinder: \(V_{DNA} = \pi \times \left(\frac{d}{2}\right)^2 \times L\), where \(d\) is the diameter and \(L\) is the length of the DNA.
Calculate the volume of the viral head, which is a sphere, using the formula: \(V_{head} = \frac{4}{3} \pi \times \left(\frac{D}{2}\right)^3\), where \(D\) is the diameter of the viral head.
Compare the volume of the DNA molecule (\(V_{DNA}\)) with the volume of the viral head (\(V_{head}\)). If \(V_{DNA} \leq V_{head}\), then the DNA can fit inside the viral head assuming complete flexibility; otherwise, it cannot.
Provide a conclusion based on the comparison, justifying mathematically whether the DNA molecule fits inside the viral head.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Molecular Dimensions and Volume
Understanding the physical size of the DNA molecule involves calculating its volume based on length and diameter. DNA is modeled as a cylinder, so volume is found using the formula π × (radius)^2 × length. Converting units consistently is essential to compare DNA volume with the viral head volume.
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Volume of a Sphere
The viral head is a sphere, and its volume is calculated using the formula (4/3)πr³, where r is the radius. Knowing the viral head's volume allows comparison with the DNA volume to determine if the DNA can physically fit inside.
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Concept of Molecular Flexibility and Packing
Assuming complete flexibility means the DNA can bend and coil without volume change, allowing it to occupy space efficiently. This assumption lets us focus on volume comparison rather than shape constraints, simplifying the problem to whether the DNA volume is less than or equal to the viral head volume.
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Related Practice
Textbook Question
Contrast the structure of SINE and LINE DNA sequences. Why are LINEs referred to as retrotransposons?
Textbook Question
Mammals contain a diploid genome consisting of at least 10⁹ bp. If this amount of DNA is present as chromatin fibers, where each group of 200 bp of DNA is combined with 9 histones into a nucleosome and each group of 6 nucleosomes is combined into a solenoid, achieving a final packing ratio of 50, determine:
(a) the total number of nucleosomes in all fibers,
(b) the total number of histone molecules combined with DNA in the diploid genome, and
(c) the combined length of all fibers.
Textbook Question
How many base pairs are in a molecule of phage T2 DNA 52-µm long?
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Textbook Question
The human genome contains approximately 106 copies of an Alu sequence, one of the best-studied classes of short interspersed elements (SINEs), per haploid genome. Individual Alu units share a 282-nucleotide consensus sequence followed by a 3'-adenine-rich tail region [Schmid (1998)]. Given that there are approximately 3 x 109 base pairs per human haploid genome, about how many base pairs are spaced between each Alu sequence?
Textbook Question
The following is a diagram of the general structure of the bacteriophage chromosome. Speculate on the mechanism by which it forms a closed ring upon infection of the host cell.